Many mechanical systems make use of motors that move objects into different positions. In general, an actuating element, such as a motor, has a drive input that mates with an input coupling of a tool to be actuated. Various mechanical structures may be used to engage the drive input with the input coupling. One example is a boss and pocket structure. Specifically, the drive input may include a disc that has a boss extending from the surface of the disc. The boss may be designed to fit into a corresponding pocket on a disc connected to the input coupling. When the boss is successfully positioned within the pocket, rotation of the drive input causes rotation of the input coupling, which in turn causes movement of the tool.
A mechanical system that involves engaging a drive input with an input coupling may be a teleoperative medical system. The teleoperative medical system may include motors with drive inputs that couple to and operate interchangeable medical instruments. In some embodiments, the drive inputs of the motors include drive discs that engage with corresponding instrument discs on the medical instrument. Each of the instrument discs may actuate a different type of motion in the medical instrument. For example, one disc may control actuating members that change the roll position of the instrument. Other discs may control actuating members that change the yaw, pitch, or grip of the medical instrument. When an interchangeable instrument is connected to the teleoperative medical system, each of the drive discs on the arm must be appropriately engaged with the instrument discs so that the actuating elements will drive movement of the medical instrument as desired.
When the instrument discs are first placed against the drive discs of the motors, the instrument discs may not be precisely aligned with the drive discs. The drive discs may be rotated until they fall into the corresponding pockets of the instrument discs. In some cases, the bosses may not engage the pockets properly on the first rotational pass, but may engage properly on a subsequent rotational pass. Before a medical procedure may be performed, confirmation that the drive discs have appropriately engaged the instrument discs is needed.